New Calidus/MTOsport rotor hub and new blades

[Gyro_Kai]

Hello,

in the below thread we discussed the cracks showing on some rotorblades at the end-point of the, possibly too stiff, hub bar mount.

http://www.rotaryforum.com/forum/showthread.php?t=27399

I now got to fly the new rotor hub. Coincidentially I could fly it on an MTOsport, even though the blades were the heavier Calidus blades (orange caps). The hub, of course makes no difference to the flying properties.

From flying perspective these heavier blades simply fly better:
I only had time for a few T&Gs but they climbed like mad. I cought myself actively raising my body away from the back-rest, afraid I might fall out backwards.
RRPMs were 10-20 lower at every flight stage but it went up to Vne (100mph) not sweat. I am really impressed. I lost a little weight, but not that much :).

Additionally the blades were very smooth, very little stickshake.
Another novelty was the new 2-stage exhaust, which pushes the noise from nearly 68 dBa down below 62 dBa.

Will do some more testing next month.

Pictures of the new hub-bar and exhaust enclosed.

Kai.

[WillyRose]

Kai,
Are the new hub/blades and exhaust are produced by the factory for the MTOsport?
Any idea of price?
Regards,
Clive

[Gyro_Kai]

Yes, blades and exhaust are produced at the factory. If you send in your rotor head you get it re-done for around 3500 Euros was what I overheard. Exhaust, I don't know, but can ask tomorrow.

Kai.

[flyer912]

My MT came with the two stage exhaust, I cut the second stage off, less weight and hardly noticable extra noise, a bit more throaty maybe.
Baz

[Mike G]

Kai
The 68 and 62 dBA are measured at what distance and under what conditions? Giving noise values can be very decieving unless you give the appropriate conditions. Measured at 1 meter (inustrial standard) or 100 meters doesn't give the same value.
Mike G

[Gyro_Kai]

The excerpt for noise test reads as follows:

4.5.1.5 Das Referenz-Flugverfahren muss auf folgende meteorologische Referenzbedingungen
bezogen werden:
a) Luftdruck in Meereshöhe 101,325 kPa,
b) Umgebungstemperatur in Meereshöhe 15°C, d.h. ISA,
c) relative Luftfeuchtigkeit 70 %,
d) kein Wind.
4.5.2 Referenz-Flugverfahren
4.5.2.1 Der Lärmmesspunkt muss in stabilisierter Steigflugkonfiguration in einer Höhe
zwischen 75 m (246 ft) und 150 m (492 ft) über Grund überflogen werden. Die Fluggeschwindigkeit
soll die für bestes Steigen vy (Toleranz ± 5 km/h (± 3 kt)) sein, bei höchstzulässiger
Motorleistung und höchstzulässiger Drehzahl.
Anmerkung: Diese Leistung wird, sofern Lufttüchtigkeitsforderungen nicht entgegen stehen,
erreicht:
a) bei Ultraleichtflugzeugen mit Festpropellern mit Vollgas,
b) bei Ultraleichtflugzeugen mit Verstellpropellern mit Vollgas und höchstzulässiger
Drehzahl,
c) bei Ultraleichtflugzeugen mit Ladermotoren und Verstellpropellern mit höchstzulässigem
Ladedruck und höchstzulässiger Drehzahl.


Flight conditions:

a) air pressure 101,325 kPa,
b) Temperature on MSL 15°C, i.e. ISA,
c) relative humidity 70 %,
d) no Wind.

Flight procedure

The measuring point must be overflown in maximum climb configuration between 75 m (246 ft) and 150 m (492 ft).
Velocity adjusted to best climb, motor at full power. This translates to:

full throttle on fixed pitch props
full throttle and max. allowed rpm on adjustable prop
max. manifold pressure and max. rpm on adjustable prop and charged motor.


Kai.

[Mike G]

Kai
A noise source that measured 68 dBA at 75 m will measure 62 dBA at 150 metres under the same conditions. I'm afraid you test is pretty meaningless as defined above.
Mike

[Gyro_Kai]

I don't make the rules, I only quote them. This is from the German rulebook.

Kai.

[Mike G]

Kai
I wasn't getting at you, just telling you to take any information about noise with a pinch of salt. Very few people really understand noise values and what they mean. I've done quite a bit of noise testing and results are often meaningless because of all the variables. I once heard one very experienced noise expert proclaim that a specific noise level was 82 dBA plus or minus the day of the month and that just about covers the accuraccy of noise measurements.
From what I've read most of the noise from a prop driven a/c comes from the prop, even classic tractor a/c. Pushers are ten times worse because the prop is cutting into such a turbulant airflow. If you want to reduce noise on a classic pusher gyro you need to get as much distance as possible between the blade (especially the tips) and any fixed part of the gyro. For that the Magnis are terrible with only about 1 inch between the tip and the tail boom. I keep saying one of these days I'll try to reduce the noise level but I no longer have access to a good noise meter.
Mike G

[ckurz7000]

The excerpt for noise test reads as follows:


Flight conditions:

a) air pressure 101,325 kPa,
b) Temperature on MSL 15°C, i.e. ISA,
c) relative humidity 70 %,
d) no Wind.

Flight procedure

The measuring point must be overflown in maximum climb configuration between 75 m (246 ft) and 150 m (492 ft).
Velocity adjusted to best climb, motor at full power. This translates to:

full throttle on fixed pitch props
full throttle and max. allowed rpm on adjustable prop
max. manifold pressure and max. rpm on adjustable prop and charged motor.


Kai.

Kai, this is only half the story. You are right in that is the correct flight procedure. But the noise level measured thus must be corrected to the reference height by a specified formula. So you don't win if you fly higher.

-- Chris.

[Gyro_Kai]

oh yes, I should have read the entire document.

The corrective delta, added to the measured sound level is:

D=20 x log (H/Hr)

H= actual height over measuring point
Hr= reference height.

Kai.